Geographical information model of carbon monoxide dispersion near expressways affected by traffic under different conditions of atmospheric stabilities (A case study: Niayesh expressway) نویسندگان [English]

One of the main sources of air pollution in metropolitan areas is the traffic and the associated problems in the transportation system. Traffic network development and increasing the number of different types of vehicles with different speeds, leading possibility of incomplete fuel burning, can increase air pollutant concentration which is often inevitable; moreover, has endangered the health of civilian in cities. Accordingly, air pollution modeling to predict spatial concentration of air pollutants across the cities is required. In this research, a case study of carbon monoxide emission, near Niayesh expressway in Tehran megacity, for duration of 23rd October 2015 to 21st November 2015, has been conducted. This research is carried out by using CALINE4 software, presenting the results upon GIS-based methods. The CO concentration across the selected domain is predicted at different points by the distance of 500 m at the sides of expressway axis considering different atmospheric stability classes. The results are affected by path geometric of expressway, traffic data and weather conditions during the study period. The proposed model calibration has been obtained by predicting model results with some measured point values. The results of the proposed model have presented the CO pollutant concentration increase in the areas affected along the wind direction, especially in the north side of the expressway while there is stabilized atmosphere and wind speed is decreasing. Furthermore, the CO concentration is remained at minimum level along opposite wind direction. The predicted pollution concentrations with increasing distance from the expressway show  exponentially reduction trend and have been decreased at distances of 25, 100, 150, and 300 meters from expressway axis as 18%, 48%, 57%, 73%, and 96%, respectively.  In this study, the CO concentration in GIS system was predicted, for duration of 23rd October 2015 to 21st November 2015, which is the most stable period of atmospheric condition. The obtained results represent that the CO concentration along two zones of Valiasr street to Seoul street and Farahzadi Boulevard to Ashrafi Esfahani highway are more than the rest. Accordingly, the conditions of two named zones are introduced as high hazardous zones which are in need of pollutant reduction by the changes in boundary conditions.